Method of assembly for fan drive gear system with rotating carrier

ABSTRACT

A method of assembling a fan drive gear system for a gas turbine engine according to an example of the present disclosure includes the steps of providing a unitary carrier defining a central axis and that includes spaced apart walls and circumferentially spaced mounts defining spaced apart apertures at an outer circumference of the carrier, gear pockets defined between the walls and extending to the apertures, and a central opening in at least one of the walls. The method includes the steps of inserting a plurality of intermediate gears through the central opening, moving the intermediate gears radially outwardly relative to the central axis into the gear pockets, inserting a sun gear through the central opening, moving the plurality of intermediate gears radially inwardly relative to the central axis to engage the sun gear, and coupling a fan shaft to the carrier such that the fan shaft and intermediate gears are rotatable about the central axis. A fan drive gear system is also disclosed.

BACKGROUND

This application relates to fan drive gear systems, and moreparticularly to assembly of a fan drive gear system having an epicyclicgear train with a rotating carrier that can be incorporated in a gasturbine engine to drive a turbo fan.

Gas turbine engines may employ an epicyclic gear train connected to aturbine section of the engine, which is used to drive the turbo fanthrough an output shaft. In a typical epicyclic gear train, a sun gearreceives rotational input from a turbine shaft through a turbine shaft.A carrier supports intermediate gears that surround and mesh with thesun gear. A ring gear surrounds and meshes with the intermediate gears.In arrangements in which the carrier is fixed against rotation, theintermediate gears are referred to as “star” gears and the ring gear iscoupled to the output shaft that drives the turbo fan. In arrangementsin which the ring gear is fixed against rotation, the intermediate gearsare referred to as “planetary” gears and the carrier is coupled to theoutput shaft that drives the turbo fan. The output shaft can besupported by a bearing assembly. The bearing assembly and gear traininclude rotatable components that require lubrication during operation.

The carrier housings are typically split along a central plane, withassembly of the gear train including bringing together and securing thehalves of the carrier housing. For improved strength and rigidity, ascompared with a two-part housing, it is desirable for an epicyclic geartrain to have a unitary carrier housing.

SUMMARY

A method of assembling a fan drive gear system for a gas turbine engineaccording to an example of the present disclosure includes the steps ofproviding a unitary carrier defining a central axis and that includesspaced apart walls and circumferentially spaced mounts defining spacedapart apertures at an outer circumference of the carrier, gear pocketsdefined between the walls and extending to the apertures, and a centralopening in at least one of the walls. The method includes the steps ofinserting a plurality of intermediate gears through the central opening,moving the intermediate gears radially outwardly relative to the centralaxis into the gear pockets, inserting a sun gear through the centralopening, moving the plurality of intermediate gears radially inwardlyrelative to the central axis to engage the sun gear, and coupling a fanshaft to the carrier such that the fan shaft and intermediate gears arerotatable about the central axis.

In a further embodiment of any of the foregoing embodiments, the step ofcoupling the fan shaft includes attaching a torque frame to the carriersuch that the torque frame is rotatable about the central axis.

In a further embodiment of any of the foregoing embodiments, the torqueframe has a plurality of axially extending fingers which are receivedwithin slots defined by one of the walls of the carrier, at locationscircumferentially intermediate locations of the intermediate gears.

A further embodiment of any of the foregoing embodiments includesplacing a ring gear includes a first ring half and a second ring gearhalf on an outer periphery of the sun gears to engage the intermediategears, including moving the first ring gear half such that the firstring gear half does not block radially inwardly extending apertures in aradially outer surface of the carrier, and moving pins into theapertures to lock the fingers within the slots, and then moving thefirst ring gear half over the apertures. The second ring gear half isplaced on the intermediate gears subsequent to the locking of thefingers within the slots.

In a further embodiment of any of the foregoing embodiments, the torqueframe defines a frustro-conical geometry including a first end portionattached to the carrier and that tapers toward a second end portioncoupled to the fan shaft.

In a further embodiment of any of the foregoing embodiments, the torqueframe is integral with the fan shaft.

A further embodiment of any of the foregoing embodiments includesplacing a ring gear on an outer periphery of the sun gears to engage theintermediate gears, moving the carrier along an engine longitudinalaxis, fixedly attaching the ring gear to an engine static structure, andcoupling a fan shaft to the carrier such that the fan shaft andintermediate gears are rotatable about the engine longitudinal axis.

In a further embodiment of any of the foregoing embodiments, the step offixedly attaching the ring gear includes interconnecting the ring gearand the engine static structure with a flexible support.

A further embodiment of any of the foregoing embodiments includesinterconnecting the sun gear and a turbine shaft with a flexible inputcoupling, and securing the fan shaft to a fan hub that supports aplurality of fan blades.

A further embodiment of any of the foregoing embodiments includes movinga first tapered bearing assembly along the engine longitudinal axis toposition the first tapered bearing assembly about an outer periphery ofthe fan shaft.

A further embodiment of any of the foregoing embodiments includes movinga lubricant transfer bearing assembly along the engine longitudinal axisto position the lubricant transfer bearing about the outer periphery ofthe fan shaft, the lubricant transfer bearing assembly for transferringlubricant between the fan shaft and a bearing support, moving alubricant manifold to interconnect the lubricant transfer bearingassembly and a plurality of journal bearings that support theintermediate gears, and moving a second tapered bearing assembly alongthe engine longitudinal axis to position the second tapered bearingassembly about the outer periphery of the fan shaft such that thelubricant transfer bearing assembly is between the first and secondtapered bearing assemblies.

A further embodiment of any of the foregoing embodiments includes movingthe bearing support along the central axis to support the first andsecond tapered bearing assemblies, and then fixedly attaching thebearing support to the engine static structure.

A further embodiment of any of the foregoing embodiments includesplacing a ring gear on an outer periphery of the sun gears to engage theintermediate gears, and then fixedly attaching the ring gear to anengine static structure.

In a further embodiment of any of the foregoing embodiments, the sungear and the intermediate gears are each formed as a single gear. Thering gear is formed as a two-part gear that has a first ring gear halfand a second ring gear half, and the step of placing the ring gearincludes placing each of the first ring gear half and the second ringgear half about the outer periphery of the intermediate gears.

In a further embodiment of any of the foregoing embodiments, the sungear and the intermediate gears have two spaced portions. Each of theportions have helical gear teeth, with the helical gear teeth on the twoportions extending in opposed directions. The ring gear includes tworing gear halves each having one direction of helical gear teeth, withthe helical gear teeth on the two ring gear halves extending in opposeddirections.

In a further embodiment of any of the foregoing embodiments, the step ofmoving the plurality of intermediate gears radially inwardly occursafter the step of inserting the sun gear. The step of coupling the fanshaft includes attaching a torque frame to the carrier such that thetorque frame is rotatable about the central axis, and further includesinserting journal bearings within each of the intermediate gears afterthe steps of moving the plurality of intermediate gears radiallyinwardly and attaching the torque frame.

A fan drive gear system for a gas turbine engine according to an exampleof the present disclosure include a unitary carrier that defines acentral axis and has a pair of axially spaced apart side walls, andaxially extending circumferentially spaced mounts that connect the sidewalls, a central opening in one of the walls, and circumferentiallyspaced smaller openings spaced radially outwardly of the centralopening, with internal surfaces of circumferentially spaced curved wallsof the mounts defining intermediate gear pockets that extend away fromthe central opening, and the intermediate gear pockets dimensioned toreceive intermediate gears. The intermediate gears are received throughthe central opening, and secured at a position spaced radially inwardlyof a radially outermost area in the intermediate gear pockets relativeto the central axis, with the intermediate gears having teeth engagedwith teeth of a sun gear received in the central opening. A ring gear isreceived at radially outer locations such that ring gear teeth engageteeth of the intermediate gears, and a torque frame interconnects thecarrier and a fan shaft such that the fan shaft and intermediate gearsare rotatable about the central axis.

In a further embodiment of any of the foregoing embodiments, the torqueframe has a plurality of axially extending fingers received within slotsdefined by one of the walls of the carrier, at locationscircumferentially intermediate locations of the intermediate gears, andpins inwardly of radially inwardly extending apertures in a radiallyouter surface of the carrier. The pins lock the fingers within theslots, with the ring gear received radially outwardly of the radiallyinwardly extending apertures. The torque frame is integral with the fanshaft, and defines a frustro-conical geometry that has a first endportion attached to the carrier and that tapers toward a second endportion coupled to the fan shaft.

A further embodiment of any of the foregoing embodiments includes aflexible support interconnecting the ring gear and an engine staticstructure, and a flexible input coupling interconnecting the sun gearand a turbine shaft. The fan shaft drives a fan hub that supports aplurality of fan blades.

A further embodiment of any of the foregoing embodiments includes pairof tapered bearing assemblies about an outer periphery of the fan shaft,the pair of tapered bearings attached to a bearing support, and alubricant transfer bearing assembly between the pair of tapered bearingassemblies and that transfers lubricant between the fan shaft and thebearing support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a gas turbine engine.

FIG. 2 is a cross-sectional view of a fan drive gear system including anepicyclic gear train and a shaft assembly.

FIG. 3A shows a unitary carrier.

FIG. 3B illustrates an end view of the epicyclic gear train taken alongline 3B-3B in FIG. 2 with intermediate gears and a star gear in aninstallation position.

FIG. 4 is an enlarged view of a portion of the epicyclic gear train ofFIG. 3 with the sun gear and intermediate gears shown in phantom.

FIG. 5A is an enlarged view of a portion of the epicyclic gear train ofFIG. 2.

FIG. 5B is another enlarged view of a portion of the epicyclic geartrain of FIG. 2.

FIG. 6 illustrates sun and intermediate gears being inserted into thecarrier of FIG. 3A.

FIG. 7 illustrates portions of a gear.

FIG. 8A illustrates an assembly step.

FIG. 8B illustrates a subsequent assembly step.

FIG. 8C illustrates another subsequent assembly step.

FIG. 8D illustrates a torque frame.

FIG. 8E illustrates a subsequent assembly step.

FIG. 8F illustrates another subsequent assembly step.

FIG. 9 illustrates assembly steps of a fan drive gear system includingmounting the epicyclic gear train of FIG. 2.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath B whilethe compressor section 24 drives air along a core flowpath C forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines including three-spool architectures.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisA relative to an engine static structure 36 via several bearing systems37. It should be understood that various bearing systems 37 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 is connected to the fan 42 through ageared architecture 48 to drive the fan 42 at a lower speed than the lowspeed spool 30. The high speed spool 32 includes an outer shaft 50 thatinterconnects a high pressure compressor 52 and high pressure turbine54. A combustor 56 is arranged between the high pressure compressor 52and the high pressure turbine 54. A mid-turbine frame 57 of the enginestatic structure 36 is arranged generally between the high pressureturbine 54 and the low pressure turbine 46. The mid-turbine frame 57further supports bearing systems 37 in the turbine section 28. The innershaft 40 and the outer shaft 50 are concentric and rotate via bearingsystems 37 about the engine central longitudinal axis A which iscollinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than ten (10), the gearedarchitecture 48 is an epicyclic gear train, such as a planetary gearsystem or other gear system, with a gear reduction ratio of greater thanabout 2.3 and the low pressure turbine 46 has a pressure ratio that isgreater than about 5. In one disclosed embodiment, the engine 20 bypassratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout 5:1. Low pressure turbine 46 pressure ratio is pressure measuredprior to inlet of low pressure turbine 46 as related to the pressure atthe outlet of the low pressure turbine 46 prior to an exhaust nozzle.The geared architecture 48 may be an epicycle gear train, such as aplanetary gear system or other gear system, with a gear reduction ratioof greater than about 2.5:1. It should be understood, however, that theabove parameters are only exemplary of one embodiment of a gearedarchitecture engine.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram ° R)/(518.7°R)]^(0.5). The “Low corrected fan tip speed” as disclosed hereinaccording to one non-limiting embodiment is less than about 1150ft/second.

The engine 20 is provided with a fan gear drive system 27 that includesthe geared architecture 48 and a shaft assembly 43 driven by an outputof the geared architecture 48. The shaft assembly 43 includes a fanshaft 21 mechanically attached or otherwise secured to a fan hub 45 thatsupports a plurality of fan blades (one shown) of the fan 42. One of thebearing systems 37 is coupled to a bearing support 12 that at leastpartially surrounds the fan shaft 21. The bearing system 37 includes oneor more bearing assemblies 29, 31 that support the fan shaft 21.

FIG. 2 illustrates a fan drive gear system 127 that can be incorporatedinto a gas turbine engine, such as the engine 20 of FIG. 1. The gearedarchitecture 48 of FIG. 1 may be assembled as described below for geartrain 122. The gear train 122 can be incorporated in the fan drive gearsystem 127 to drive a shaft assembly 143. Assembly of the fan drive gearsystem 127, including mounting the gear train 122 and shaft assembly 143to engine static structure 36 of the engine 20, are described below. Inthe example arrangement, the epicyclic gear train 122 is a planetarygear train including a stationary or fixed ring gear 138 and a carrier134 that rotates with a fan 142 about the engine longitudinal axis Aduring operation of the engine 20. Other epicyclic gear trains canbenefit from the teachings herein, including a star arrangement.

The epicyclic gear train 122 includes a sun gear 128 that is connectedto an input or turbine shaft 123, which provides rotational input, by asplined connection 130. Turbine shaft 123 can be mechanically attachedto or form a portion of inner shaft 40 (FIG. 1), for example, to drivethe sun gear 128.

The gear train 122 defines a central axis X extending through the sungear 128 that can be parallel or collinear with the engine longitudinalaxis A. The carrier 134 supports planetary or intermediate gears 132that are coupled to the sun gear 128 by meshed interfaces 126 betweenthe teeth of the sun gear 128 and the intermediate gears 132.

A ring gear 138 surrounds the carrier 134 and is coupled to theintermediate gears 132 by meshed interfaces 144. The ring gear 138 is atwo-part ring gear formed by first and second ring gear halves 138A/Bthat can be symmetrical. In alternative examples, the ring gear 138 isformed as a single gear. The ring gear 138 is fixedly attached to aportion of the engine static structure 36, such as a housing or bearingsupport 112. The ring gear 138 grounds the gear train 122 to the enginestatic structure 36 such that the ring gear 138 is fixed againstrotation about the engine longitudinal axis A during operation of theengine 20.

A flexible input coupling 125 can interconnect the sun gear 128 and theturbine shaft 123. A flexible support 141 can interconnect the ring gear138 and the bearing support 112. The flexible input coupling 125 andflexible support 141 can include one or more respective undulations125A, 141A that deflect to permit rotation and axial movement of thegear train 122 relative to the turbine shaft 123 and/or engine staticstructure 36 which may be caused by rotational and axial loads from thefan 142, for example. The ring gear halves 138A/B and flexible support141 can be mechanically attached by a connection 139 including one ormore fasteners. The flexible support 141 can at least partially surroundthe carrier 134 when in an installed position. The flexible support 141can selectively engage or contact a deflection limiter 147. Thedeflection limiter 147 can be defined by one or more slots in the enginestatic structure 36, for example, that engage surfaces of the flexiblesupport 141 to bound circumferential and/or radial movement of the geartrain 122. In alternative examples, the flexible input coupling 125and/or the flexible support 141 are omitted, with the sun gear 128interconnected to the turbine shaft 123 and/or the ring gear halves138A/B attached to the engine static structure 36.

The shaft assembly 143 includes a turbo fan shaft 121 coupled to thecarrier 134 such that the fan shaft 121 and intermediate gears 132 arerotatable about the central axis X. The carrier 134 is fixedly attachedto the fan shaft 121 by a torque frame 136. The fan shaft 121 ismechanically attached or otherwise secured to a fan hub 145 thatsupports a plurality of fan blades (one shown) of the fan 142. Thecarrier 134 and torque frame 136 are rotatable about the central axis Xto provide rotational output to the fan shaft 121 to drive the fan 142.The fan hub 145 is mechanically attached to and supported by an outerperiphery of the fan shaft 121.

Bearing system 137 includes at least one bearing assembly to support thefan shaft 121. In the illustrated example of FIG. 2, bearing system 137includes a first bearing assembly 129 and a second bearing assembly 131forward of the gear train 122 to support rotation of the fan shaft 121.Each of the bearing assemblies 129, 131 includes a carrier and bearing.The assemblies 129, 131 can be tapered roller bearing assemblies thatare arranged to counteract radial and thrust loads, for example.

The bearing support 112 can be coupled to a lubricant passage 113 forcommunicating lubricant between a fluid source FS and the bearing system137. The bearing system 137 includes a stationary lubricant transferbearing assembly 133 for transferring lubricant between the fan shaft121 and the bearing support 112.

The bearing assemblies 129, 131, 133 are arranged or positioned about anouter periphery of the fan shaft 121 such that bearing assembly 133 isaxially between bearing assemblies 129, 131. The bearing assemblies 129,131 can be axially spaced apart by a flexible spacer 117, which canprovide a preload on the bearings assemblies 129, 131. The flexiblespacer 117 can include at least one undulation 117A to permit axiallymovement between the bearings assemblies 129, 131, and defines anaperture 117B for receiving a feeder tube 115.

The feeder tube 115 extends from the bearing support 112 is fluidlycoupled to the lubricant transfer bearing assembly 133. The feeder tube115 communicates lubricant supplied from the lubricant passage 113 tothe bearing assembly 133. The bearing assembly 133 includes openings133A that supply lubricant to an outer periphery of the fan shaft 121.The openings 133A can be races defined in an inner periphery of thebearing assembly 133 that extend through in the fan shaft 121 andcommunicate lubricant with a plurality of passages 121A. The passages121A can be substantially axially aligned with the openings 133A.

The lubricant transfer bearing assembly 133 is fluidly coupled to alubricant manifold 135 including interconnected conduits or segments135A/B/C that define internal fluid passages for communicating lubricantbetween the bearing support 112 and the gear train 122. In theillustrated example of FIG. 2, the segment 135B is a jumper tube thatinterconnects axially extending segment 135A and radially outwardlyextending segment 135C. Lubricant from the passages 121A is supplied tothe first segment 135A, and then to the other segments 135B/135C. Fromthe third segment 135C of the lubricant manifold 135, lubricant issupplied to a respective journal bearing 164 for distribution to otherportions of the gear train 122. The arrangement of the lubricanttransfer bearing assembly 133 and lubricant manifold 135 can deliverrelatively high pressure lubricant to the journal bearings 164, such asabove about pounds per square inch (PSI), or more narrowly between about200-300 PSI. In this example, a single set of segments 135A/B/C isshown. However, a plurality of the segments 135A/B/C can be utilized tocommunicate lubricant to different parts of the gear train 122.

The torque frame 136 is mechanically attached to the carrier 134. Asshown in FIG. 8E, the carrier 134 includes connecting structure definingmounts 154 having a plurality of apertures or slots 156 receiving aplurality of elongated fingers 230 of the torque frame 136, with pins148 extending through spherical bearings 146 and bushings 152 securingthe fingers 230 to the carrier 134. Fasteners 150 retain the pins 148 tothe carrier 134, also shown in FIG. 8E. The torque frame 136interconnects the carrier 134 and the fan shaft 121 such that the fanshaft 121 and intermediate gears 132 are rotatable about the enginelongitudinal axis A.

Referring to FIGS. 3A and 3B, with continued reference to FIG. 2, thecarrier 134 can be a unitary structure constructed or manufactured fromone piece for improved structural strength, rigidity and integrity, ascompared with two-part housings. Carrier 134 is centered on the centralaxis X. Carrier 134 includes axially spaced apart side walls 160 thatare interconnected by the circumferentially spaced and axially extendingconnecting structure defining mounts 154, which are generallywedge-shaped members. The mounts 154 and side walls 160 are unitary withone another. That is, these components are fixed, such as by beingwelded or cast as a unitary structure, prior to assembly of the geartrain 122. The mounts 154 have opposing curved surfaces 158 that are inclose proximity to the intermediate gears 132 and generally follow thecurvature of the teeth of the intermediate gears 132 to guide lubricanton the curved surfaces 158 toward the intermediate gears 132 foradditional lubrication.

The mounts 154 are circumferentially spaced about the carrier 134 todefine apertures 198 through which the intermediate gears 132 extend toengage the ring gear 138. The side walls 160 include holes 162 forreceiving respective journal bearings 164 that support each of theintermediate gears 132. Each journal bearing 164 is retained within thecarrier 134 by retainers 166 fastened to the side walls 160.

The carrier 134 defines a central opening 200 along the central axis X.The central opening 200 can be machined in at least one of the sidewalls 160 and defines gear pocket 204 for receiving the sun gear 128.The central opening 200 is dimensioned to accommodate insertion of thesun gear 128 and each of the intermediate gears 132. Intermediate gearpockets 202 can be machined between the side walls 160 and mounts 154for each of the intermediate gears 132 and form circumferentiallydistributed apertures 198 at an outer circumference of the carrier 134.The intermediate gear pockets 202 are dimensioned to receive respectiveintermediate gears 132. The mounts 154 can be circumferentially spacedabout the carrier 134 at a distance that is less than a width of thegears 128, 132 such that the gear pockets 202, 204 can only be accessedthrough the central opening 200, which can provide improved strength andrigidity of the carrier 134.

Referring to FIG. 4, oil baffles 168 can be arranged between the sidewalls 160 near each of the mounts 154. The baffles 168 include ends 172that abut the mounts 154. The baffles 168 include opposing curvedsurfaces 170 arranged in close proximity to the intermediate gears 128.The curved surfaces 158, 170 can be contiguous with and adjoin oneanother, and define the gear pockets 202 that are dimensioned to receiverespective intermediate gears 132. The gear pocket 204 is definedbetween a surface 173 of each of the baffles 168 opposite the ends 172and is dimensioned to receive the sun gear 128.

Each of the side walls 160 includes holes 174 that receive fasteners 176which secure the baffles 168 to the carrier 134 (see also FIG. 5B). Thebaffles 168 establish a lubrication passage provided by a primarypassage 186 that fluidly communicates with the lubricant manifold 135.The baffles 168 can include openings 182 that receive a respectivesegment 135C (FIG. 2) of the lubricant manifold 135 that extends througha hole 183 in the side wall 160. The primary passage 186 is incommunication with first and second passages 188, 190 that spraylubricant on the teeth of the sun and intermediate gears 128, 132. Thepassages 188, 190 can be arranged about ninety degrees from one another,for example. Lubricant distribution is integrated into the baffles 168so that separate components can be eliminated, which can reduce weightand complexity of the gear train 122. The baffles 168 can be constructedfrom the same or a different, relatively lighter weight material thanthe carrier 134.

Referring to FIGS. 5A and 5B, which are sectional views of the geartrain 122, segment 135A of the lubricant manifold 135 is mechanicallyattached to the torque frame 136. Segment 135B spans between thesegments 135A/C. An end portion of segment 135C extends through anopening of the wall 160 of the carrier 134 and communicates lubricantbetween the fluid source FS and the journal bearing 164, as shown inFIG. 5A. An end portion of another segment 135C extends through anotheropening of the wall 160 of the carrier 134 and communicates lubricantbetween the fluid source FS and the baffle 168, as shown in FIG. 5B. Asshown in FIG. 5B, the baffle 168 can include passages 186, 188, 190 forspraying or otherwise communicating lubricant to the sun gear 128 (seealso FIG. 4). Although FIGS. 5A and 5B show only one set of segments135A/B/C communicating fluid with the journal bearing 164 and anotherset of segments 135A/B/C communicating fluid with the baffle 168, itshould be appreciated that the lubricant manifold 135 can have aplurality of segments 135A/B/C each fluidly coupled to a respectivejournal bearing 164 or baffle 168.

Returning to FIG. 3B, and with reference to FIG. 6, the intermediategears 132 are inserted into the central opening 200 and moved radiallyoutwardly relative to the central axis X such that the intermediategears 132 extend through the apertures 198 and can be positioned inabutment with the mounts 154 (position indicated by dashed lines in FIG.3B). In this position, there is an adequate gap (t) between the teeth ofadjacent intermediate gears 132 to accommodate a width (w) of the ends172 of the adjacent baffles 168. After the baffles 168 have beeninserted, the sun gear 128 can be inserted into the central opening 200.The intermediate gears 132 can then be moved radially inwardly relativeto the central axis X to mesh with the sun gear 128. The baffles 168 aresecured to the carrier 134 using fasteners 176 (FIG. 4). The tubes 180can be inserted and the rest of the lubricant distribution system can beconnected.

As mentioned above, the intermediate gears 132 are initially insertedwithin the central hole 200 for the sun gear 128. The intermediate gears132 are moved radially outwardly relative to the central axis X, and thebaffles 168 are inserted. The sun gear 128 is then inserted, and theintermediate gears 132 can then be moved radially inwardly relative tothe central axis X to engage the sun gear 128. All of this assemblyoccurs with the carrier 134 already formed as a unitary structure.

Referring to FIG. 7, each of the intermediate gears 132 can have twotoothed portions 300, 302, which have helical gear teeth extending inopposed directions. A recess or central area 304 is formed between thetoothed portions 300, 302. The outer perimeter of the sun gear 128 canhave a complementary profile to mate with the toothed portions 300, 302and establish the meshed interfaces 126 (FIG. 2). Each of the first andsecond ring gear halves 138A/B can mate with a respective one of the twogear teeth directions of the toothed portions 300, 302 to establish themeshed interfaces 144 (FIG. 2).

As shown in FIG. 8A, once the sun gear 128 and intermediate gears 132are brought in engagement, the journal bearings 164 can be insertedwithin the intermediate gears 132. As shown in FIG. 8B, the first ringgear half 138A can then be moved onto the outer periphery of theintermediate gears 132. FIG. 8C illustrates the first ring gear half138A in an installed position.

FIG. 8D is a perspective view of the torque frame 136 according to anexample. The torque frame 136 includes a body 136A extending between afirst end portion 136B and a second, opposed end portion 136B. The body136A defines a generally frustro-conical geometry with the first endportion 136B tapering toward second end portion 136C.

The fingers 230 extend away from the first end portion 136B to attach orotherwise secure the torque frame 136 to the carrier 134. The second endportion 136C is coupled to the fan shaft 121 (portion shown forillustrative purposes). In the illustrated example of FIG. 8D, thetorque frame 136 is integral with the fan shaft 121. In alternativeexamples, the torque frame 136 and the fan shaft 121 are separate anddistinct components that are mechanically attached to each other.

FIG. 8E illustrates the first ring gear half 138A moved axially suchthat the first ring gear half 138A does not align with the apertures 220in the mounts 154, which are to receive respective pins 148 of thetorque frame 136. Once each pin 148 has been moved inwardly to lock therespective finger 230 within the slot 156 of the carrier 134 to securethe torque frame 136 to the carrier 134, then the first ring gear half138A can be moved back axially over a portion of the aperture 220.

As shown in FIG. 8F, the next step is to mount the second ring gear half138B, completing assembly of the gear train 122. At each step, all ofthe components of the gear train 122 are secured in some manner. An oilgutter can then be installed.

FIG. 9 illustrates steps for assembling and mounting the fan drive gearsystem 127 to the engine static structure 36 and to the fan 142. Oncethe gear train 122 is assembled, the gear train 122 including carrier134 is moved along the engine longitudinal axis A. The flexible support141 can be fixedly attached to and moved together with the ring gear138. The fan shaft 121 can be moved together with the torque frame 136along the engine longitudinal axis A (or central axis X), or can beseparately attached to the torque frame 136. The fan shaft 121 isfixedly attached or otherwise coupled to the carrier 134 such that thefan shaft 121 and intermediate gears 132 are rotatable about the enginelongitudinal axis A. The lubricant manifold 135 can be mechanicallyattached or otherwise secured to the carrier 134 and/or fan shaft 121prior to securing the torque frame 136 to the carrier 134.

Once the gear train 122 is positioned, the shaft assembly 143 includingbearing system 137 can then be mounted to the gear train 122 andgrounded to the engine static structure 36. The first bearing assembly129 is moved along the engine longitudinal axis A to position the firstbearing assembly 129 about an outer periphery of the fan shaft 121. Inother examples, the first bearing assembly 129 is situated on the outerperiphery of and moved together with the fan shaft 121.

The bearing support 112 is moved along the engine longitudinal axis Aand brought into abutment with bearing assembly 129. The bearingassembly 129 can be mechanically attached to the bearing support 112with one or more fasteners. Then the bearing support 112 is fixedlyattached to the engine static structure 36 and the flexible support 141such that the gear train 122 is grounded to the bearing support 112.

The lubricant transfer bearing assembly 133 is moved along the enginelongitudinal axis A to position the bearing assembly 133 about the outerperiphery of the fan shaft 121. The second bearing assembly 131 is thenmoved along the engine longitudinal axis A to position the secondbearing assembly 131 about the outer periphery of the fan shaft 121,with the bearing assembly 133 axially between the bearing assemblies129, 131. Then fan shaft 121 is mechanically attached or otherwisesecured to the fan hub 145.

The disclosed arrangement provides a technique for assembling a fandrive gear system including an epicyclic gear train such as a planetarysystem having a unitary carrier housing. The disclosed gear train, asconfigured and assembled as disclosed herein, has an improved strength,integrity and rigidity.

It should be understood that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like arewith reference to the normal operational attitude of the vehicle andshould not be considered otherwise limiting.

Although the different examples have the specific components shown inthe illustrations, embodiments of this disclosure are not limited tothose particular combinations. It is possible to use some of thecomponents or features from one of the examples in combination withfeatures or components from another one of the examples. Althoughparticular step sequences are shown, described, and claimed, it shouldbe understood that steps may be performed in any order, separated orcombined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A method of assembling a fan drive gear systemfor a gas turbine engine comprising the steps of: providing a unitarycarrier defining a central axis and that includes spaced apart walls andcircumferentially spaced mounts defining spaced apart apertures at anouter circumference of the carrier, gear pockets defined between thewalls and extending to the apertures, and a central opening in at leastone of the walls; inserting a plurality of intermediate gears throughthe central opening; moving the intermediate gears radially outwardlyrelative to the central axis into the gear pockets; inserting a sun gearthrough the central opening; moving the plurality of intermediate gearsradially inwardly relative to the central axis to engage the sun gear;coupling a fan shaft to the carrier such that the fan shaft andintermediate gears are rotatable about the central axis, includingattaching a torque frame to the carrier such that torque frame isrotatable about the central axis; wherein the torque frame includes aplurality of axially extending fingers which are recieved within slotsdefined by one of the walls of the carrier, at locationscircumferentially intermediate locations of the intermediate gears;wherein the torque frame defines a frustro-conical geometry including afirst end portion attached to the carrier and that tapers toward asecond end portion coupled to the fan shaft; wherein the torque frame isintegral with the fan shaft; placing a ring gear including a first ringgear half and a second ring gear half on an outer periphery of theintermediate gears to engage the intermediate gears, including movingthe first ring gear half such that the first ring gear half does notblock radially inwardly extending apertures in a radially outer surfaceof the carrier; and moving pins into the apertures to lock the fingerswithin the slots, and then moving the first ring gear half over theapertures, wherein the second ring gear half is placed on theintermediate gears subsequent to the locking of the fingers within theslots; and fixed attaching the ring gear to an engine static structuresubsequent to the placing step, including interconnecting the ring gearand the engine static structure with a flexible support.
 2. The methodas recited in claim 1, further comprising: moving the carrier along anengine longitudinal axis; and coupling the fan shaft to the carrier suchthat the fan shaft and intermediate gears are rotatable about the enginelongitudinal axis.
 3. The method as recited in claim 2, furthercomprising: interconnecting the sun gear and a turbine shaft with aflexible input coupling; and securing the fan shaft to a fan hub thatsupports a plurality of fan blades.
 4. The method as recited in claim 3,further comprising moving a first tapered bearing assembly along theengine longitudinal axis to position the first tapered bearing assemblyabout an outer periphery of the fan shaft.
 5. The method as recited inclaim 4, further comprising moving a lubricant transfer bearing assemblyalong the engine longitudinal axis to position the lubricant transferbearing about the outer periphery of the fan shaft, the lubricanttransfer bearing assembly for transferring lubricant between the fanshaft and a bearing support; moving a lubricant manifold to interconnectthe lubricant transfer bearing assembly and a plurality of journalbearings that support the intermediate gears; and moving a secondtapered bearing assembly along the engine longitudinal axis to positionthe second tapered bearing assembly about the outer periphery of the fanshaft such that the lubricant transfer bearing assembly is between thefirst and second tapered bearing assemblies.
 6. The method as recited inclaim 5, further comprising: moving the bearing support along thecentral axis to support the first and second tapered bearing assemblies,and then fixedly attaching the bearing support to the engine staticstructure.
 7. The method as recited in claim 1, wherein the sun gear andthe intermediate gears are each formed as a single gear, the ring gearis formed as a two-part gear including the first ring gear half and thesecond ring gear half.
 8. The method as recited in claim 7, wherein thesun gear and the intermediate gears have two spaced portions, with eachof the portions having helical gear teeth, with the helical gear teethon the two portions extending in opposed directions, the ring gearincludes two ring gear halves each having one direction of helical gearteeth, with the helical gear teeth on the two ring gear halves extendingin opposed directions.
 9. The method as recited in claim 1, wherein: thestep of moving the plurality of intermediate gears radially inwardlyoccurs after the step of inserting the sun gear; and further comprisinginserting journal bearings within each of the intermediate gears afterthe steps of moving the plurality of intermediate gears radiallyinwardly and attaching the torque frame.
 10. A fan drive gear system fora gas turbine engine comprising: a unitary carrier defining a centralaxis and having a pair of axially spaced apart side walls, and axiallyextending circumferentially spaced mounts that connect the side walls, acentral opening in one of the walls, and circumferentially spacedsmaller openings spaced radially outwardly of the central opening, withinternal surfaces of circumferentially spaced curved walls of the mountsdefining intermediate gear pockets that extend away from the centralopening, and the intermediate gear pockets dimensioned to receiveintermediate gears; wherein the intermediate gears are received throughthe central opening, and secured at a position spaced radially inwardlyof a radially outermost area in the intermediate gear pockets relativeto the central axis, with the intermediate gears having teeth engagedwith teeth of a sun gear received in the central opening; a ring gearreceived at radially outer locations such that ring gear teeth engageteeth of the intermediate gears, where in the ring gear includes a firstring gear half and a second ring gear half on an outer periphery of theintermediate gears such that the first ring gear half and the secondring gear half engage the intermediate gears; and a torque frameinterconnecting the carrier and a fan shaft such that the fan shaft andintermediate gears are rotatable about the central axis; wherein thetorque frame includes a plurality of axially extending fingers receivedwithin slots defined by one of the walls of the carrier, at locationscircumferentially intermediate locations of the intermediate gears, andpins inwardly of radially inwardly extending apertures in a radiallyouter surface of the carrier, the pins locking the fingers within theslots, with the ring gear received radially outwardly of the radiallyinwardly extending apertures; and wherein the torque frame is integralwith the fan shaft, and defines a frustro-conical geometry including afirst end portion attached to the carrier and that tapers toward asecond end portion coupled to the fan shaft; and a flexible supportinterconnecting the ring gear and an engine static structure.
 11. Thesystem as recited in claim 10, further comprising: a flexible inputcoupling interconnecting the sun gear and a turbine shaft; and whereinthe fan shaft drives a fan hub that supports a plurality of fan blades.12. The system as recited in claim 10, further comprising: a pair oftapered bearing assemblies about an outer periphery of the fan shaft,the pair of tapered bearings attached to a bearing support; and alubricant transfer bearing assembly between the pair of tapered bearingassemblies and that transfers lubricant between the fan shaft and thebearing support.
 13. The system as recited in claim 10, wherein the sungear and the intermediate gears have two spaced portions, with each ofthe portions having helical gear teeth, with the helical gear teeth onthe two portions extending in opposed directions, the first and secondring gear halves each having one direction of helical gear teeth, withthe helical gear teeth on the first and second ring gear halvesextending in opposed directions.